Researchers have been working to increase storage density and reduce storage cost of information storage devices such as magnetic hard -drives, optical drives, and semiconductor random access memory. However, increasing the storage density is becoming increasingly difficult. Conventional technologies appear to be approaching fundamental limits on storage density. For instance, information storage based on conventional magnetic recording is rapidly approaching fundamental physical limits such as the superparamagnetic limit, below which a magnetic bit is not stable at room temperature.
Information storage devices that do not face these fundamental limits are being researched and developed. One such device, an atomic resolution storage device, includes multiple electron emitters having electron emission surfaces that are proximate a storage medium. During a write operation, an electron emitter changes the state of a submicron-sized storage area on the storage medium by bombarding the storage area with a relatively high intensity electron beam having an appropriate pulse shape and amplitude. The storage medium is either in a polycrystalline state or an amorphous state. By changing the state of the storage area, a bit is written to the storage area.
Another such device is a thermal random access memory (RAM). Thermal RAMs are cross point memories that use current to change the state of a storage area (cell) located at the cross point of two conductors in an array. A typical thermal RAM cell includes a storage area that is either in a polycrystalline state or an amorphous state. By changing the state of the storage area, a bit is written to the storage area. A programming current to drive the state (i.e., phase) change is in the range of a few milli-amperes. A large area transistor is used to support the programming current.
There is a need for a non-volatile semiconductor storage device, having a lower programming current relative to Thermal RAM, with increased storage capacity.